BA7781

Video ICs Stereo microphone amplifier for camcorders BA7781K The BA7781K allows construction of a stereo-microphone amplifier for camcorder use with a minimum number of external components. The IC has a built-in wind-noise detection circuit, and wind-noise rejection filter. The filter circuit is controlled automatically. The IC can operate off a 3.0V power supply. •Applications Camcorders •Features off a 3.0V to 5.25V power supply. 1) Operates 2) Automatic wind-noise rejection circuit. 3) Matrix circuit for stereo emphasis. 4) Automatic switching circuit for external microphones, built-in external monaural decision circuit, and input switch mode decision circuit. •Block diagram MTX OUT L PRE OUT L INV OUT L MTX IN L MODE 24 HPF IN L 18 WND 15dB DET NOR INV IN L 24 EXT IN L 25 EXT BG 26 INT IN L 27 GND REG GND 28 VREG 29 INT 23 22 21 20 19 17 16 DET OUT 15 DET IN 14 BIAS BIAS VCC 13 VCC 12 LPF INV OUT – + 13dB + MIX – 10dB EXT +– BIAS INT IN R 30 RIPL 31 INT OUT L 11 LPF INV IN 10 MIX OUT 09 MIC MONO 08 OUT R EXT 13dB NOR WND 06 MTX OUT R EXT IN R 32 EXT 01 MODE 1 02 PRE OUT R 03 INV IN R 04 INV OUT R + – 05 MTX IN R 15dB 07 HPF IN R 1 Video ICs BA7781K •Absolute maximum ratings (Ta = 25°C) Parameter Power supply voltage Power dissipation Operating temperature Storage temperature Symbol VCC Pd Topr Tstg Limits 7.0 400∗ – 10 ~ +70 – 55 ~ +125 Unit V mW °C °C •Recommended operating conditions (Ta = 25°C) Parameter Power supply voltage Symbol VCCS Min. 3.0 Typ. — Max. 5.25 Unit V CC ∗ Reduced by 4mW for each increase in Ta of 1°C over 25°C. •Electrical characteristics (unless otherwise noted, Ta = 25°C and V Parameter Current dissipation 1 Current dissipation 2 Preamplifier gain Output amplifier gain Distortion Maximum output voltage Output noise voltage Input switch separation Interchannel separation Internal microphone power supply voltage Input switch control voltage Symbol I INT IEXT VGPR VGOA THD Vom VNO CTI→E CTL← →R = 3.3V) Unit mA mA dB dB % Vrms dBV dB dB V V V Conditions INT MIC IN, L / Rch No dissipation by mic EXT MIC IN, L / Rch No dissipation by mic 30 / 32pin→2pin GAIN 27 / 25pin→23pin GAIN 3 / 6 / 7pin→8pin GAIN 22 / 19 / 18pin→17pin GAIN INT / EXT, Vo = 300mVrms, L / Rch∗2 INT / EXT MIC IN, L / Rch f = 1kHz (distortion 1%∗2 ) INT / EXT, L / Rch, Rg = 1kΩ When gain is 28dB∗1 INT→EXT MIC IN, Rg = 1kΩ, L / Rch (distortion 1%∗2 ) , when gain is 28dB∗1 INT / EXT MIC, Lch→Rch, Rg = 1kΩ (distortion 1%∗2 ) , when gain is 28dB∗1 Pin 27 output voltage for 30kΩ load “H”level, 1 / 24 pin DC “L” level, 1 / 24 pin DC Input 80Hz signal to pin 15, and measure gain at switch off side.∗1 Min. — — 12 14 — 0.85 — — — 2.3 1.6 0 Typ. 5.0 4.8 13 15 0.05 1.1 – 90 – 88 – 61 2.5 — — Max. 8.0 8.0 14 16 0.3 — – 80 – 70 – 50 2.75 VCC 0.6 VREG VHSWH VHSWL High-pass filter switching attenuation characteristic VGHON — — – 30 dB VGHOFF VHON High-pass filter control voltage VHOFF — 2.5 0 — — — – 30 VCC 0.3 dB V V 15pin – 29.0dBV IN (80Hz) 6 / 19pin – 25.5dBV IN (1kHz) 6→8pin / 19→17pin GAIN 15pin – 45.0dBV IN (80Hz) 7 / 18pin – 25.5dBV IN (1kHz) 7→8pin / 18→17pin GAIN HPF on holding voltage (pin 16) HPF off holding voltage (pin 16) ∗1 JIS-A filter used. ∗2 400Hz to 30kHz filter used. 2 Video ICs BA7781K •Pin descriptions Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Pin name MODE 1 PRE OUT R INV IN R INV OUT R MTX IN R MTX OUT R HPF IN R OUT R MIC MONO MIX OUT LPF INV IN LPF INV OUT VCC BIAS DET IN DET OUT OUT L HPF IN L MTX OUT L MTX IN L INV OUT L INV IN L PRE OUT L MODE 24 EXT IN L BG INT IN L GND VREG INT IN R RIPL EXT IN R Function Mode control 1 input Preamplifier output Inverter input Inverter output Matrix amplifier input Matrix amplifier output High-pass filter input Signal output External microphone monaural decision signal output Mix Output Low-pass filter block inverter input Low-pass filter block inverter output VCC Bias voltage Detector circuit input Detector circuit output Signal output High-pass filter input Matrix amplifier output Matrix amplifier input Inverter output Inverter input Preamplifier output Mode control 24 input External microphone input For regulator ripple filter capacitor Internal microphone input GND Regulator output Internal microphone input For bias ripple filter capacitor External microphone input Voltage (V) — 1.65 1.65 1.65 1.65 1.65 1.65 1.65 — 1.65 — — 3.3 1.65 1.65 — 1.65 1.65 1.65 1.65 1.65 1.65 1.65 — 1.65 1.25 1.65 — 2.5 1.65 1.65 1.65 Circuit 25kΩ EF (P - P) 100kΩ EF (P - P) B EF (P - P) 100kΩ C (P - P) C EF (P - P) B EF (P - P) — EF (P - P) 2kΩ 22kΩ C (P - P) 100kΩ EF (P - P) B EF (P - P) 100kΩ EF (P - P) 25kΩ 75kΩ 10kΩ 75kΩ — C 75kΩ 50kΩ 75kΩ ∗ EF: emitter follower, P-P: push pull, B: base, and C: collector. All numerical values are standardized values. 3 Video ICs BA7781K •Measurement circuit MODE 24 HPF IN SW2 10k 10.5k 0.1µ NOR 1 0.1µ 2 2200p 18 17 16 DET + 0.1µ 0.1µ EXT IN Lch INT IN + 24 25 26 27 28 EXT 23 22 21 20 19 2.2µ 1M L OUT – + 13dB INT WND 15dB 15 14 10µ 0.1µ 30k 0.1µ + 10µ 0.1µ VCC GND + MIX – REG EXT 10dB GND BIAS VCC 13 12 29 BIAS INT IN Rch EXT IN + – 200k 11 10 30 + EXT 200k 0.1µ INV (11) IN 31 INT 32 EXT 1 NOR WND 10µ 0.1µ 13dB + – 2 3 4 5 6 15dB 7 8 9 0.1µ 0.1µ 10k 10.5k 0.1µ R OUT 2200p 2 1 SW1 MODE 1 HPF IN UNITS RESISTOR: Ω CAPACITOR: F Fig. 1 4 Video ICs BA7781K •Application example UNITS RESISTOR: Ω CAPACITOR: F B' A' 15k 10k 10.5k 0.022µ 100k 2200p L OUT 2.2µ 0.1µ 0.1µ EXT IN L ch INT IN + 0.1µ 21 20 19 NOR 0.022µ 18 WND 15dB 24 25 26 27 EXT 23 22 17 16 24k + – + 13dB 1M DET INT 15 14 + 10µ REG 0.1µ 28 GND + MIX – EXT 10µ VCC 10dB GND 29 BIAS BIAS VCC + – 13 12 2200p 220k INT IN R ch EXT IN 0.1µ 30 + EXT 11 100k 13dB NOR WND 150k 0.01µ 10µ 0.1µ 31 32 INT EXT 10 + – 2 3 4 5 6 100k 15dB 7 8 0.022µ 9 0.01µ MIC-MONO 1 24k 0.1µ 0.1µ 10k 10.5k 0.022µ 100k R OUT 2200p A B 15k Additional components INT / EXT monitoring INT / EXT L OPEN 100k 12 1µ + ∗1) When using the matrix circuit connect A-A' and B-B'. ∗2) The pin 10 and 12 low-pass filter components are for fc = 150Hz, Gain = 0dB, 18dB / oct. Fig. 2 5 Video ICs BA7781K •Measurement circuit switch table (blank cells: no spesification) Parameter Current dissipation 1 Current dissipation 2 Preamplifier gain Output amplifier gain Distortion Maximum output Output noise voltage Input switch separation (INT→ EXT) INT EXT Internal microphone power supply voltage Input switch control voltage SW1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 High-pass filter control voltage 1 2 SW2 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 2 H Vth H H H H Vth L L L L L INT, EXT INT, EXT INV (11) , HPF INV (11) , INT INV, 16pin of Vth HPF, 16pin of Vth L H L L L L INT INT EXT MODE1 H MODE24 L Signal input pin Conditions other than No. 1 Interchannel separation High-pass filter switching attenuation characteristic ∗ H and L are VCC and GND levels. Measure the voltage range that maintains the mode for Vth. •Operation notes rejection circuit (1) Automatic wind-noise The MAX OUT (pin 10) signal passes through the three-stage low-pass filter connected between pins 10 and 12, and the DC level of the low-frequency signal component is detected. This DC voltage (pin 16 DC voltage) automatically controls the on / off switching of the high-pass filter. The components connected to pins 11 and 12 set the gain of a multiple-feedback-type twostage low-pass filter constructed around an inverting amplifier, and by changing the gain of the circuit you can adjust the detection sensitivity. It is also possible to switch the high-pass filter manually by applying a DC voltage to pin 16 (see Fig 2). (2) Additional compornents for INT / EXT monitor use An internal circuit sets pin 12 to roughly the bias potential in INT mode, and to GND for EXT mode. This switches the external transistor on and off for INT and EXT modes respectively. This can be used to indicate whether the microphone amplifier is operating with the INT or EXT input. In the case of a camcorder, this can be used to display a massage such as “EXT MIC ON” in the EVF. 6 Video ICs BA7781K •Electrical characteristic curves 16PIN DETECT OUTPUT: VDETOUT (V) OUTPUT LEVEL: VROUT (dBV) VCC = 3.3V Input: 80Hz Ta = 25°C 0 2.5 2.0 VCC = 3.3V Input: 80Hz Ta = 25°C – 20 NOR side output 6→8pin HPF side output 7→8pin 1.5 – 40 1.0 0.5 – 60 – 60 – 50 – 40 – 30 – 20 – 10 0 – 60 – 50 – 40 – 30 – 20 – 10 15PIN INPUT SIGNAL LEVEL: VDETIN (dBV) 15PIN INPUT SIGNAL LEVEL: VDETIN (dBV) Fig. 3 HPF switching characteristics Fig. 4 Detector voltage characteristis •External dimensions (Units: mm) 9.0 ± 0.3 7.0 ± 0.2 24 9.0 ± 0.3 7.0 ± 0.2 25 17 16 0.4 0.15 ± 0.1 0.15 32 1 8 9 1.45 ± 0.1 0.05 0.8 0.4 ± 0.1 QFP32 7